Messages in this thread | | | Subject | Re: Bad kfree of dma_parms in v5.7-rc5 | From | Tomi Valkeinen <> | Date | Wed, 20 May 2020 12:18:26 +0300 |
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Hi Marek,
On 20/05/2020 12:13, Marek Szyprowski wrote: > Hi Tomi, > > On 20.05.2020 11:00, Tomi Valkeinen wrote: >> Commit 9495b7e92f716ab2bd6814fab5e97ab4a39adfdd ("driver core: >> platform: Initialize dma_parms for platform devices") v5.7-rc5 causes >> at least some v4l2 platform drivers to break when freeing resources. >> >> E.g. drivers/media/platform/ti-vpe/cal.c uses >> vb2_dma_contig_set_max_seg_size() and >> vb2_dma_contig_clear_max_seg_size() to manage the dma_params, and >> similar pattern is seen in other drivers too. >> >> After 9495b7e92f716ab2, vb2_dma_contig_set_max_seg_size() will not >> allocate anything, but vb2_dma_contig_clear_max_seg_size() will still >> kfree the dma_params. >> >> I'm not sure what's the proper fix here. A flag somewhere to indicate >> that vb2_dma_contig_set_max_seg_size() did allocate, and thus >> vb2_dma_contig_clear_max_seg_size() must free? >> >> Or drop the kzalloc and kfree totally, if dma_params is now supposed >> to always be there? > > Thanks for reporting this issue! > > Once the mentioned commit has been merged, the code should assume that > the platform devices does have a struct dma_params allocated, so the > proper fix is to alloc dma_params only if the bus is not a platform bus: > > if (!dev_is_platform(dev) && !dev->dma_parms) { > dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL); > > same check for the free path.
There is also "amba: Initialize dma_parms for amba devices". And the commit message says PCI devices do this too.
Guessing this based on the device type doesn't sound like a good idea to me.
Tomi
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